Allwinner SRAM for smp bringup:
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------------------------------------------------
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Allwinner's A80 SoC uses part of the secure sram for hotplugging of the
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primary core (cpu0). Once the core gets powered up it checks if a magic
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value is set at a specific location. If it is then the BROM will jump
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to the software entry address, instead of executing a standard boot.
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Therefore a reserved section sub-node has to be added to the mmio-sram
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declaration.
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Note that this is separate from the Allwinner SRAM controller found in
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../../sram/sunxi-sram.txt. This SRAM is secure only and not mappable to
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any device.
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Also there are no "secure-only" properties. The implementation should
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check if this SRAM is usable first.
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Required sub-node properties:
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- compatible : depending on the SoC this should be one of:
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"allwinner,sun9i-a80-smp-sram"
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The rest of the properties should follow the generic mmio-sram discription
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found in ../../misc/sram.txt
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Example:
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sram_b: sram@20000 {
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/* 256 KiB secure SRAM at 0x20000 */
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compatible = "mmio-sram";
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reg = <0x00020000 0x40000>;
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#address-cells = <1>;
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#size-cells = <1>;
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ranges = <0 0x00020000 0x40000>;
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smp-sram@1000 {
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/*
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* This is checked by BROM to determine if
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* cpu0 should jump to SMP entry vector
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*/
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compatible = "allwinner,sun9i-a80-smp-sram";
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reg = <0x1000 0x8>;
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};
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};
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